POLARIZATION GRADIENT COOLING OF TRAPPED IONS

We report the first experimental demonstration of one-dimensional polarization gradient cooling of bound ions. The trapped particles are only weakly bound along the laser cooling axis. Nevertheless, the particle motion has to be treated quantum mechanically. The minimum kinetic energy is found when the depth of the optical potential approaches a quantum of the vibrational energy of the trapped ions. Cooling to low vibrational states of the trap has been observed. We have also produced the lowest one-dimensional temperature for an ion crystal.